Plant materials including grains contain a number of valuable components such as starch, protein, mixed linkage 1-4, 1-3 beta-D-glucan (hereinafter “beta-glucan” or “BG”), cellulose, pentosans, tocols, etc. These components, and products derived from these components, have many food and non-food uses. Consequently, there is a strong and continued industry interest for the processing of such plant materials.
Dietary fibre is generally accepted as having protective effects against a range of diseases predominant in Western developed countries including colorectal cancer, coronary heart disease, diabetes, obesity, and diverticular disease. The term ‘dietary fiber’ is commonly defined as plant material that resists digestion by the secreted enzymes of the human alimentary tract but may be fermented by the microflora in the colon. Increased fiber consumption is associated with lowering total serum cholesterol and LDL cholesterol, modifying the glycemic and insulinemic response and protecting the large intestine from disease. BG, a non-starch polysaccharide, is a water-soluble component of dietary fibre and thus contributes such health benefits.
BG has been extensively researched and has been found to have a number of positive health benefits including reducing cholesterol levels, regulating glycemic response, and immune system enhancement. In particular, consumption of beta-glucan is believed to increase the viscosity of intestinal contents, thus slowing down the movement of dietary cholesterol and glucose as well as bile acids towards the intestinal walls leading to reduced absorption. These benefits have led to the U.S. Food and Drug Administration (FDA) approving a health claim indicating that four daily servings of oat products containing 0.75 grams/serving of soluble oat fibre may reduce the risk of heart disease.
Cardio-Vascular Disease (CVD) is considered the principal cause of death in all developed countries, being responsible for 20% of deaths worldwide.1 In the United States 59.7% of people had some form of CVD in 1997,2 and in Canada, 8 million people are estimated to be suffering from CVD.3 An estimated 102 million American adults have total blood cholesterol levels of 200 milligrams per deciliter (mg/dL) and higher. Of these, about 41 million have levels of 240 mg/dL or above. In adults, total cholesterol levels of 240 mg/dL or higher are considered high risk. Levels from 200 to 239 mg/dL are considered borderline high risk. Low-density lipoprotein (LDL) cholesterol levels of 130 mg/dL or higher is associated with increased risk of coronary heart disease and occurs in approximately 45% of Americans. Approximately 18% of Americans have LDL cholesterol levels of 160 mg/dL or higher. High LDL cholesterol levels are associated with a higher risk of coronary heart disease (CHD). 1 “Cardiovascular Disease: Epidemiology” World Health Organization, Oct. 4, 2000. (Online, cited Dec. 8, 2000) Available at: http://www.who.int/ncd/cvd/cvd_epi.htm2 “Cardiovascular Disease Statistics” American Heart Association, 2000 (Online cited Nov. 23, 2000). Available at; http://www.americanheart.org/Heart_and_Stroke_A_Z_Guide/cvds.html)3 “Health Matters: Incidence of Cardiovascular Disease” Heart and Stroke Foundation of Canada, 2000. (Online, cited Nov. 28, 2000) Available at: http://heartandstroke.ca/cgi-bin/English/Catalog/Public/bR.cgi?110100:::Incedence%20of%20Cardiovascular%20Disease%20:::158981323241:::100001:110100
Not only is CVD the number one cause of death, it also is the most expensive disease in most developed countries. In the U.S. in 2002, the disease cost $329.2 billion in direct and indirect costs. Direct costs were $199.5 billion, with drug costs totaling $31.8 billion.4 Canadian cost statistics are only as recent as 1993, but at this time total CVD costs were $19.7 billion. Direct costs amounted to $7.3 billion, with drugs accounting for $1.6 billion of this total.5 These statistics demonstrate the importance of reducing the risk of CVD through dietary means. Increased consumption of soluble fiber, especially through the incorporation of beta-glucan concentrate as an ingredient into a variety of food products can contribute significantly towards this goal. However, it is crucial for the beta-glucan to have high-viscosity characteristics to achieve the claimed health benefits since there is growing evidence that links health benefits of beta-glucan to its viscosity. 4 “Economic Costs of Cardiovascular Diseases” American Heart Association, 2002. 2002 Heart and Stroke Statistical Update.5 “The Changing Face of Heart Disease and Stroke in Canada 2000” Heart and Stroke Foundation of Canada, 2000. (Online, cited Nov. 29, 2000). Available at: http://www.hc-sc.gc.ca/hbp/lddc/bcrdd/hdsc2000/index.html
Until now, BG has been restricted to high value markets such as cosmetics, medical applications, and health supplements due to the high cost of extraction, which has prohibited its use as an ingredient in the food industry. Current food products in the marketplace contain low concentrations of BG, requiring consumption of unrealistic amounts of such products in order to satisfy the parameters of the health claim.
In the extraction of BG from grains, a number of investigations at laboratory and pilot scale have been carried out on the fractionation of these grains including barley. In general, conventional processes utilize water, acidified water and/or aqueous alkali (i.e. NaOH, Na2CO3 or NaHCO3) as solvents for the slurrying of whole cracked barley, barley meal (milled whole barley) or barley flour (roller milled barley flour or pearled-barley flour). These slurries are then processed by techniques such as filtration, centrifugation and ethanol precipitation to separate a slurry into various components. This conventional process for barley fractionation has a number of technical problems and whilst realizing limited commercial feasibility has been limited by the expense of the product particularly for food applications.
In particular, technical problems arise because the beta-glucan in barley flour is an excellent water-binding agent (a hydrocolloid) and as such, upon addition of water (neutral, alkali or acidic environment), the beta-glucan hydrates and tremendously thickens (increases the viscosity) the slurry. This thickening imposes many technical problems in the further processing of the slurry into pure barley components (i.e. starch, protein, fiber, etc.), including clogging of the filter during filtration and inefficient separation of flour components during centrifugation.
Usually, these technical problems are minimized, if not eliminated, by the addition of a substantial quantity of water to the thick/viscous slurry in order to dilute and bring the viscosity down to a level where further processing can be carried out. However, the use of high volumes of water leads to several further problems including increased effluent water volumes and the resulting increased disposal costs. In addition, the beta-glucan, which solubilizes and separates with the supernatant (water) during centrifugation, is usually recovered by precipitation with ethanol. This is done by the addition of an equal volume of absolute ethanol into the supernatant. After the separation of precipitated beta-glucan, the ethanol is preferably recovered for recycling. However, recovery requires distillation, which is also a costly operation from an energy usage perspective.
Furthermore, the aqueous alkali solubilization and subsequent precipitation of beta-glucan in ethanol (and centrifugation steps in between) is believed to contribute to the breakdown of the beta-glucan chains that results in a lower-grade, lower-viscosity beta-glucan product.
Still further, the use of these past techniques also is believed to support both the growth of microorganisms and increased enzyme activity that may contribute to hydrolysis of the beta-glucan chains. These problems are particularly manifested in larger batch operations where it may become difficult to control enzyme activity and thus lead to problems of batch-to-batch consistency.
Accordingly, there is a need for efficient processes for the fractionation of grains that overcomes the particular problems of slurry viscosity and water-usage. Moreover, there is a need for a process that provides a high purity, high-viscosity beta-glucan product in a close to natural state wherein the BG product has decreased starch and protein content.
Thus, there continues to be a need for techniques which improve the yield and quality of beta-glucan products extracted from the cell walls of grains including oats and barley that overcome problems of water-based extraction techniques.
A review of the prior art reveals that beta-glucan products having improved rheological properties have not been disclosed.
Moreover, sonication/sonification/ultrasonication/ultrasonification (hereinafter “sonication”, “ultrasonication” and “US”) techniques have not been applied to processes for the extraction of beta-glucan from barley and oats in an alcohol slurry.
For example, while the use of ultrasonication has been described in the production of konnyaku powder (See Kimura, T., Sugahara, T and Goto, M. 2000. Improvement of a method for production of konnyaku powder using ultrasonic treatment. Journal of the Japanese Society for Food Science and Technology (Nippon Shokuhin Kagaku Kogaku Kaishi). 47 (8):604-612), this reference is silent with respect to the extraction of beta glucan.